Techniques for improving reliability of a fault current limiting system

ABSTRACT

Techniques for improving reliability of a superconducting fault current limiting system (SCFCL) are provided. In one particular exemplary embodiment, the techniques may be realized with a superconducting fault current limiting system (SCFCL) comprising: an input current lead and an output current lead, each current lead coupled to a power distribution/transmission network; a container; a superconductor contained in the container; a shunt disposed outside the container and in parallel with the superconductor; a cryogenic system configured to provide coolant into the container; and at least one sensor disposed near and configured to monitor at least one operating condition of at least one of the input current lead and the output current lead, the superconductor, and the shunt.

PRIORITY

The present application claims a priority to U.S. Provisional PatentApplication Ser. No. 61/495,201, filed on Jun. 9, 2011, entitled“Technique For Improving Reliability Of A Fault Current LimitingSystem.” The present application also claims a priority to U.S.Provisional Patent Application Ser. No. 61/495,197, filed on Jun. 9,2011, entitled “Technique For Improving Reliability Of A Fault CurrentLimiting System.” Both of the U.S. Provisional Patent Application Ser.No. 61/495,201, and the U.S. Provisional Patent Application Ser. No.61/495,197 are incorporated herein by reference in entirety.

FIELDS

Present disclosure relates to system for limiting transmission of faultcurrent, more particularly to a technique for improving reliability of asystem for limiting transmission of fault current.

BACKGROUND

A fault current is generally defined as a temporary and substantialsurge in the current transmitted along a power transmission/distributionnetwork. The fault current may be caused by any number of events,including a lightning strike, downed power lines, or a catastrophicfailure of one or more components in the network, which results inlocalized grounding. When such events occur, a large load appears. Thenetwork, in response, may deliver a large amount of current or the faultcurrent to this load. This fault current may exceed the capacity of someof the components in the network and destroy the components. One way tominimize the effect of the fault current is to incorporate a faultcurrent limiter (FCL), which may limit the transmission of the faultcurrent. Ideally, the fault current limiter is fast acting, respondingwithin a few milliseconds of the fault condition. In addition, thecurrent limiter should be self-resetting, allowing normal current to betransmitted after the fault condition subsides.

Examples of FCL may include circuit breakers or fuses. During a faultcondition, the circuit breaker mechanically opens the network anddisrupts further fault current transmission. This system, althougheffective, may not be fast acting or self-resetting. In particular,there are significant limits to how fast a circuit breaker can open. Inthe presence of an inductive load, an arc will develop between thecontacts and continue to carry current even after the components are notin contact. Also, the circuit breaker must be closed after the faultcondition subsides. If fuses are used, the fuses may have to be replacedmanually.

Another example of the conventional FCL is an inductive fault currentlimiter (IFCL) 100 shown in FIG. 1. The conventional IFCL 100 maycomprise first and second steel cores 102 a and 102 b, an AC circuit104, and a superconducting circuit 106. As shown in the figure, The ACcircuit 104 is wound around the outer limbs of the first and secondcores 102 a and 102 b. Moreover, the superconducting circuit 106 iswound around the inner limb of each core 102 a and 102 b. Generally, thefirst and second cores 102 a and 102 b may be made out of steel or othersaturable magnetic materials.

In operation, AC current is transmitted through AC circuit 104. At thesame time, DC current flows through the superconducting circuit 106 thatis wound around the inner limb of the first and second cores 102 a and102 b. During normal conditions, DC current flowing through thesuperconducting circuit 106 maintains the cores 102 a and 102 b atmagnetic saturation, and minimum inductance will be exhibited by the ACcircuit 104. During fault conditions, the fault current flowing throughthe AC circuit 104 take the cores 102 a and 102 b out of magneticsaturation. As a result, the AC circuit may exhibit large inductanceopposing further increase of the AC current flowing through the ACcircuit. Through this process, the transmission of the fault currentflowing through the AC circuit 104, and the entire IFCL 100, may bereduced.

Another example of the conventional FCL is a superconducting faultcurrent limiter (SCFCL). Generally, the SCFCL contains a superconductingcircuit which is maintained below critical temperature level T_(c),critical magnetic field level B_(c), and critical current level I_(c).In addition, the SCFCL includes a shunt that is in parallel with thesuperconducting circuit. During normal operation, the SCFCL exhibitsalmost zero resistivity, and the current from the network is directed tothe superconducting circuit and transmitted through the SCFCL withalmost zero resistivity. During a fault condition, at least one of thetemperature, magnetic field, and current is raised above the criticallevel. In response, the superconducting circuit is quenched, and theresistance of the circuit and the SCFCL surges. As a result, the faultcurrent is directed to the shunt. As the shunt introduces resistance, acurrent with much lower amplitude exits the SCFCL. The SCFCL isdesirable as the system is fast-acting and self-resetting after thefault condition.

Among others, the reliability is an important requirement of any faultcurrent limiting systems. Any defects in the systems may preventtransmission of normal current during normal conditions, making thesystem highly inefficient. The defects may also prevent the systems fromeffectively limiting the transmission of a fault current. Accordingly, anew technique for improving reliability of fault current limiting systemis needed.

SUMMARY

Techniques for improving reliability of a superconducting fault currentlimiting system (SCFCL) are provided. In one particular exemplaryembodiment, the techniques may be realized with an superconducting faultcurrent limiting system (SCFCL) are provided. In one particularexemplary embodiment, the technique may be realized with a SCFCL systemcomprising: an input current lead and an output current lead, eachcurrent lead coupled to a power distribution/transmission network; acontainer; a superconductor contained in the container, one end of thesuperconductor being connected to the input current lead and another endof the superconductor connected to the output current lead; a shuntdisposed outside the container and in parallel with the superconductor,the first end of the shunt being connected to the input current lead anda second end of the shunt being connected to the output current lead; acryogenic system configured to provide coolant into the container,wherein the coolant is configured to maintain temperature of thesuperconductors below critical temperature of the superconductor; and atleast one sensor disposed near and configured to monitor at least oneoperating condition of at least one of the input current lead and theoutput current lead, the superconductor, and the shunt.

In accordance with other aspects of this particular exemplaryembodiment, the SCFCL system may further comprise a controller coupledto the at least one sensor, the controller receiving a signal indicativeof the operating condition of the at least one of the input current leadand the output current lead, the superconductor, and the shunt

In accordance with additional aspects of this particular exemplaryembodiment, the at least one sensor comprises a plurality of temperaturesensors, and the plurality of temperature sensors being disposed neardifferent regions of the superconductors, each sensor capable ofmonitoring temperature of different regions of the superconductor.

In accordance with further aspects of this particular exemplaryembodiment, the at least one sensor may comprise a pressure sensorcapable of monitoring pressure within the container.

In accordance with additional aspects of this particular exemplaryembodiment, the at least one sensor may comprise a plurality of sensorsproximate to different regions of the superconductor.

In accordance with further aspects of this particular exemplaryembodiment, the at least one sensor may comprise voltmeter.

In accordance with additional aspects of this particular exemplaryembodiment, the at least one sensor may comprise a current transducer.

In accordance with other aspects of this particular exemplaryembodiment, the coolant may be in liquid form, and the at least onesensor comprises at least one sensor capable of measuring level ofcoolant inside the container.

In accordance with further aspects of this particular exemplaryembodiment, the at least one sensor may be a gauss meter configured tomonitor magnetic field around the superconductor.

In accordance with additional aspects of this particular exemplaryembodiment, the at least one sensor may be capable of monitoringvibration of the superconductor induced by normal current transmittedthrough the superconductor during normal condition.

The present disclosure will now be described in more detail withreference to exemplary embodiments thereof as shown in the accompanyingdrawings. While the present disclosure is described below with referenceto exemplary embodiments, it should be understood that the presentdisclosure is not limited thereto. Those of ordinary skill in the arthaving access to the teachings herein will recognize additionalimplementations, modifications, and embodiments, as well as other fieldsof use, which are within the scope of the present disclosure asdescribed herein, and with respect to which the present disclosure maybe of significant utility.

BRIEF DESCRIPTION OF THE FIGURES

In order to facilitate a fuller understanding of the present disclosure,reference is now made to the accompanying drawings, in which likeelements are referenced with like numerals. These drawings should not beconstrued as limiting the present disclosure, but are intended to beexemplary only.

FIG. 1 illustrates a conventional inductive fault current limiter.

FIGS. 2 a and 2 b illustrate a superconducting fault current limiter(SCFCL) with a monitoring system to improve reliability according to oneembodiment of the present disclosure.

FIG. 3 illustrates an exemplary method for improving the reliability ofSCFCL according one embodiment of the present disclosure.

FIG. 4 illustrates another exemplary method for improving reliability ofSCFCL according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

Herein several embodiments of a novel technique for improvingreliability of a system for limiting transmission of fault current aredisclosed. The technique may be used to check the health of one or morecomponents in a fault current limiting system. In addition, thetechnique may be used to predict the lifetime of the components. Herein,the term “lifetime” may refer to as additional fault current a componentin the fault current system may encounter without failing. For thepurpose of clarity and simplicity, the present disclosure may focus on asuperconductor fault current limiter (SCFCL). Those of ordinary skill inthe art will recognize that the embodiments included in the presentdisclosure are for illustrative purpose only and that the embodimentsmay be equally applicable to other types of systems for limitingtransmission of a fault current. Other types of systems for limitingtransmission of a fault current may include an inductive fault currentlimiter, as described earlier, a solid state fault current limiter(SSFCL), and others.

Referring to FIG. 2, there is shown an exemplary SCFCL system 200according to one embodiment of the present disclosure. The SCFCL system200 may comprise a container 202 supported by a support 204. The SCFCLsystem 200 may also comprise input/output current leads 206 a and 206 bthat electrically couple the SCFCL system 200, and/or componentstherein, to the transmission/distribution network via the network cable104. In particular, current may be introduced into the SCFCL 200 via theinput current lead 206 a and exit the SCFCL system 200 via the outputcurrent lead 206 b.

Within the container 202, a superconducting circuit 220 may be disposed.The superconducting circuit 220 may be electrically coupled to thenetwork cable 10 via the input and output current leads 206 a and 206 b.The superconducting circuit 220 may be immersed in coolant, in gaseousor liquid form, which is used to maintain the superconducting circuit220 at a desired temperature. An example of the coolant may be liquidnitrogen. However, other types of coolant may be used as the coolant.The coolant may be provided into the container from a cryogenic system210. Outside the container 202, there may be a shunt 230 that is inparallel with the superconducting circuit 220.

The superconducting circuit 220 may comprise two or more superconductors222 disposed in parallel, and connected to one another by a connector224. In the present disclosure, each superconductor 222 may be in a formof the tape, wire, cable, etc. Although two or more superconductors 222are preferred, the present disclosure does not preclude thesuperconducting circuit 120 from comprising a single superconductor 222.In addition, the present disclosure does not preclude two or moresuperconductors 222 being connected to one another in series, with orwithout the connectors 224 therebetween.

The container 202, meanwhile, may be made from an electricallyconducting material. However, the present disclosure does not precludethe container 202 being made from electrically insulating or dielectricmaterial. The container 202 may be maintained at a ground potential or anon-ground potential. In one example, the container 202 may beelectrically connected to the ground. In other embodiments, thecontainer 202 may be electrically connected, either directly orindirectly, to the network cable 10 and maintained at live potential.Yet in other embodiments, the container 202 may be electricallyfloating. Depending on the desired voltage of the container 202, thesupport 204 may also be made from electrically conducting orelectrically non-conducting material.

As illustrated in FIGS. 2 a and 2 b, the SCFCL system 200 may alsocomprise a monitoring system 240. The monitoring system 240 may compriseone or more sensors 240 a disposed at different locations inside and/oroutside the container 202. Each sensor 240 a may be proximate todifferent components in the SCFCL system 200 including thesuperconductors 222 and the connectors 224 of the superconductingcircuit 220, and the shunt 230. The sensors 240 a may be connected orspaced apart from the components in the SCFCL system 200. Although notshown, there may be one or more sensors proximate to, being in contactor spaced apart from, the cryogenic system 210 and each of theinput/output current leads 206 a and 206 b. In addition, the monitoringsystem 240 may comprise a controller 242 that is coupled to the sensors240 a and that collects data from one or more sensors 240 a. In thepresent embodiment, the sensors 240 a collect data on the operatingparameters/conditions associated with each component to determine thehealth or estimate the lifetime of each component in the SCFCL system200.

In the present disclosure, various types of sensors 240 a may be used.Examples of the sensors 240 a may include the current transducers, thevoltage meters, the pressure sensors, the cryogen level sensor, thetemperature sensors, Gauss meter, etc. or a combination thereof. Thedata collected by the sensors 240 a may include the voltage, pressure,temperature, magnetic field, acoustic signature, vibration anddisplacement of the component, presence of bubbles forming near thesuperconductors 222. The sensors 240 a may collect the data usingvisual, acoustic, electrical means, or other means to monitor theparameters or conditions.

Hereinafter, several exemplary operations of the monitoring system 240are provided. Those of ordinary skill in the art will recognize that thepresent disclosures are not limited thereto. In one example, themonitoring system 240 may comprise at least one of the sensors 240 acontained in the container 202 as shown in FIG. 2 a. The sensor 240 amay measure the temperature within the container 202 at a given time,and provide the measured temperature to the controller 242. Thecontroller 242 may determine if the temperature within the container 202is above T_(c) of the superconductors 222. If the controller 242determines that the temperature is above T_(c), the controller 242 maydetermine that the cryogenic system (not shown) is operating at lessthan optimal efficiency. The controller 242 may then notify the operatorof the SCFCL system 200 to fix or replace the cryogenic system.

In another example, the monitoring system 240 may comprise a pluralityof sensors 240 a proximate to the different regions of at least one ofthe superconductors 222, as shown in FIG. 2 b. The sensors 240 a maymeasure the temperature near different regions across the superconductor222 and provide the measured temperatures to the controller 242. Basedon the measured temperature, the controller 242 may determine thepresence of temperature variations across the superconductor 242.Extreme variations may be indicative of the presence of hotspots ordefects on the superconductor 222. If the controller 242 determines thatthe number of hotspots exceeds a predetermined value, the controller 242may notify the operator of the SCFCL system 200 to replace thesuperconductor 222.

In another example, the monitoring system 240 may include at least oneadditional detector capable of measuring the pressure inside thecontainer 202. Based on the pressure measured by the detector, thecontroller 242 may determine possible leakage in the container 202 or afaulty cryogenic system. In another example, the monitoring system 240may include at least one additional detector capable of detecting thebubbles formed near the superconductors 222. In this example, thedetectors may detect the bubbles via, for example, optical or acousticmeans. However, the detector may detect the bubbles via other means. Asthe excessive formation of the bubbles may be attributable to hotspotsor other defects in the superconductors 222, the sensor, along with thecontroller 242, may determine the presence of faulty superconductors222.

Yet in another example, the monitoring system 240 may include at leastone additional detector capable of monitoring or detecting the change inthe magnetic field around the superconductors 222. The monitoring system240 may also include at least one additional sensor capable of detectingthe vibration of the superconductors 222, or displacement of thesuperconductors within the container 202. If the vibration ordisplacement of the superconductors 222 is excessive, the controller 242may alert the operator to fasten the superconductors 222 or correct theposition of the superconductors 222. Further, the monitoring system 240may include one or more sensors 240 a that are in contact with thesuperconductors 222, the connector 224 supporting the superconductors222, or the shunt. Such sensors 240 a may detect a voltage drop acrossan individual superconductor 222, the superconducting circuit 220, andthe shunt 230. A voltage drop across any one of an individualsuperconductor 222, the superconducting circuit 220, and the shunt 230may be indicative of at least one defective superconductor 222. Thesensors 240 a may also measure the peak current transmitted through thesuperconductors 222 to determine the health of the superconductors 222.

In the present disclosure, the monitoring system 240 may also detectvariations, either gradual or sudden, in the operating parametersassociated with a component over a period of time. Using the earlierexample of the monitoring system 240, at least one sensor 240 a disposednear a superconductor 222 may continually measure the temperature nearthe superconductors 222. A substantial increase in the temperature nearthe superconductor 222 may indicate an excessive number of hotspots ordefects. Upon determining an unacceptable number or level of defects,the controller 242 may notify the operator of the SCFCL system 200 ofsuch a change and instruct the operator to replace the superconductor222.

In another example, the monitoring system 240 may also detect andanalyze the number and properties of the fault current to which theSCFCL system 200 is exposed. Such information may be used to detect thehealth of the components in the SCFCL system 200. In addition, theinformation may be used to estimate the lifetime of the components.Using the earlier example, the sensors 240 a may detect one or moresudden changes in the temperature of at least one superconductor 222.The sensors 240 a may also collect information pertaining to theproperties of the encountered fault current. For example, the sensors240 a may collect information pertaining to the period during which thetemperature 240 a of the superconductor 222 is raised. Moreover, thesensors 240 a may also collect the magnitude of the increasedtemperature. The data collected by the sensor 240 a is provided to thecontroller 242. The controller 242 may then determine the number offault currents encountered by the SCFCL system 200. In addition, thecontroller 242 may analyze properties of each fault current encounteredby the SCFCL system 200. The controller 242 may then determine whetherthe superconductors 222 had withstood and survived the fault current. Ifthe controller 242 determines that the superconductors 222 had survived,the controller 242 may estimate the lifetime of the superconductors 222based on the collected data. If the controller deems that the lifetimeof the superconductor 222 is less than 1, the controller 242 may notifythe operator of the SCFCL system 200 replace the superconductors 222.

Those ordinary skilled in the art will recognize that the above examplesfocus on using the monitoring system 240 with temperature detectors 240a. The monitoring system 240 however may also comprise other sensorcapable of measuring/sensing other parameters. Such sensors may be usedby themselves or in conjunctions with the temperature detectors 240 a toaccurately determine the properties of the fault current and estimatethe lifetime of the superconductors 222.

Referring to FIG. 3, there is shown a flow chart of a method 300 formonitoring the health and estimating the lifetime of a SCFCL systemaccording to one embodiment of the present disclosure. For the purposeof clarity and simplicity, the method 300 of the present embodiment maybe described in context to the SCFCL system 200 shown in FIG. 2. Inaddition, the method 300 may be provided, for clarity and simplicity,using one or more sensors 240 a capable of collecting temperature data.However, those of ordinary skill in the art will recognize that othersensors capable of collecting data on other operating parameters, suchas the pressure, may also be used.

As illustrated in step 302, at least one sensor 240 a in the container202 may measured the temperature associated with a component therein(e.g. superconductor 222). In step 304, the measured, actual temperatureis provided to the controller 242, and the controller 242 may comparethe measured temperature and a predetermined, optimal temperature insidethe container 202. The predetermined temperature may be the temperaturebelow T_(c) of the superconductor 222. If the controller 242 determines,in step 306, that the actual temperature is within a predetermined valuerange (e.g. below T_(c)), the controller 308 may determined that thecryogenic system is operating at optimal condition. Otherwise, the causeof non-optimal operation of the cryogenic system 310 is identified instep 310.

If the cause is determined, in step 310, to be the result of damagedcryogenic system, the controller 242 may notify the operator of theSCFCL system 200 to replace or repair the faulty cryogenic system instep 314. Otherwise, as shown in step 316, the controller 242 may notifythe operator to adjust the cryogenic system such that temperature withinthe container 202 may return to a temperature below T_(c). For example,the controller 242 may determine that the cause of the actualtemperature inside the container 202 being above T_(c) may be due todepletion of the coolant. In such a case, the controller 242 may alertthe operator to replenish the coolant.

Referring to FIG. 4 there is shown a flow chart of a method 400 formonitoring the health and estimating the lifetime of a SCFCL systemaccording to another embodiment of the present disclosure. For clarityand simplicity, the method 400 may be provided in context to monitoringthe health and estimating the lifetime of one or more superconductors222 in the SCFCL system 200 shown in FIG. 2. Accordingly, the componentdescribed in FIG. 4 may be the superconductors 222.

As illustrated in FIG. 4, SCFCL system 200 may operate during normalconditions, as shown in step 402. When a fault current occurs, asillustrated in step 403, the properties of the fault current (e.g.energy, current level, the fault current duration, etc.) may bemeasured, directly or indirectly, by one or more sensors 240 a of themonitoring system 240 in step 404. For example, an increase in thetemperature of the superconductors 222 in response to the fault currentmay be measured by the sensors 240 a, and the information may be sent tothe controller 242. The controller 242 may then determine the propertiesof the fault current. In step 406, the controller 242 may determines ifthe properties of the fault current are within the operating window ofthe superconductor 222. If so, the controller 242 may conclude that thesuperconductors 222 may have withstood the fault current, and the method400 may proceed to step 408. Otherwise, the method 400 may proceed tostep 412, during which the operator of the SCFCL system 200 is notifiedto perform a maintenance procedure on the superconductors 222. In thepresent embodiment, the maintenance procedure may include replacing theexisting superconductors 222 with new superconductors 222.

In step 408, the controller 242 may estimate the lifetime of thesuperconductors 222 based on the properties of past fault currents. Ifthe controller 242 estimates, in step 410, that the lifetime of thesuperconductor 222 is less than 1 additional fault current, the methodmay proceeds to step 412, during which the operator of the SCFCL system200 is notified to perform the maintenance procedure. For example, thecontroller 242 may determine the increase in hotspots in thesuperconductor 222 as a result of the fault current. If the hotspotsexceed a predetermined level, the controller 242 may determined thatsuperconductor 242 is damaged and may not survive additional faultcurrents. The controller 242 may then notify the operator to replace thesuperconductor 222. However, if the hotspots in the superconductor 222are determined to be below the predetermined level, the controller 242may determine that the superconductor 222 may survive additional faultcurrents and the lifetime of the superconductor 222 to be greaterthan 1. The method 300 of the present embodiment may then return to step402.

After notifying the operator of the SCFCL system 200 to perform themaintenance procedure in step 412, the controller 422 may confirm if themaintenance step has actually taken place in step 414. If themaintenance procedure is confirmed, the controller 242 resets all countand stored data in step 416. Otherwise, the method 400 returns to step412 until the maintenance procedure takes place.

Several embodiments of a technique for improving reliability of a systemfor limiting transmission of fault current are disclosed. Those of theart will recognize that the present disclosure is not to be limited inscope by the specific embodiments described herein. Indeed, othervarious embodiments of and modifications to the present disclosure, inaddition to those described herein, will be apparent to those ofordinary skill in the art from the foregoing description andaccompanying drawings. Thus, such other embodiments and modificationsare intended to fall within the scope of the present disclosure.Further, although the present disclosure has been described herein inthe context of a particular implementation in a particular environmentfor a particular purpose, those of ordinary skill in the art willrecognize that its usefulness is not limited thereto and that thepresent disclosure may be beneficially implemented in any number ofenvironments for any number of purposes. Accordingly, the claims setforth below should be construed in view of the full breadth and spiritof the present disclosure as described herein.

What is claimed is:
 1. A superconducting fault current limiting system(SCFCL) with improved reliability, the SCFCL system comprising: an inputcurrent lead and an output current lead, each current lead coupled to apower distribution/transmission network; a container; a superconductorcontained in the container, one end of the superconductor beingconnected to the input current lead and another end of thesuperconductor connected to the output current lead; a shunt disposedoutside the container and in parallel with the superconductor, the firstend of the shunt being connected to the input current lead and a secondend of the shunt being connected to the output current lead; a cryogenicsystem configured to provide coolant into the container, wherein thecoolant is configured to maintain temperature of the superconductorsbelow critical temperature of the superconductor; and at least onesensor disposed near and configured to monitor at least one operatingcondition of at least one of the input current lead and the outputcurrent lead, the superconductor, and the shunt.
 2. The SCFCL systemaccording to claim 1, further comprising: a controller coupled to the atleast one sensor, the controller receiving a signal indicative of theoperating condition.
 3. The SCFCL system according to claim 2, whereinthe at least one sensor comprises a plurality of temperature sensors,and the plurality of temperature sensors being disposed near differentregions of the superconductors, each sensor capable of monitoringtemperature of different regions of the superconductor.
 4. The SCFCLsystem according to claim 2, wherein the at least one sensor comprises apressure sensor capable of monitoring pressure within the container. 5.The SCFCL system according to claim 1, wherein the at least one sensorcomprises a plurality of sensors proximate to different regions of thesuperconductor.
 6. The SCFCL system according to claim 1, wherein the atleast one sensor comprises voltmeter.
 7. The SCFCL system according toclaim 1, wherein the at least one sensor comprises a current transducer.8. The SCFCL system according to claim 1, wherein the coolant is inliquid form, and wherein at least one sensor comprises at least onesensor capable of measuring level of coolant inside the container. 9.The SCFCL system according to claim 1, wherein the at least one sensoris a gauss meter configured to monitor magnetic field around thesuperconductor.
 10. The SCFCL system according to claim 1, wherein theat least one sensor is capable of monitoring vibration of thesuperconductor induced by normal current transmitted through thesuperconductor during normal condition.